Learn about the advantages and applications of electron microscopy (TEM & SEM), essential tools for exploring structures at the atomic and nanoscales.
Have you ever wondered how scientists see the viruses or atoms, molecules?
This is possible only because of the Electron Microscopy, which is a very important tool that goes far beyond light microscope or optical microscopes.
What is Electron Microscopy?
Electron Microscopy is useful for fast moving electrons to obtain a high-resolution image of an object. electrons have very short wavelength, so this technique is used for obtaining images thousands of times clearer than obtained by a normal light microscope.
Definition⇒ Electron Microscopy is a modern advanced technique in which instead of light, an electron beams are used to observe high resolution images of very tiny particles, cells and their structures.
How does Electron Microscope work –
- Electron Microscope has an electron gun. this electron gun emits a beam of many electrons.
- This beam is placed on the samples of any object.
- Electromagnetic lenses focus the beam.
- When the beam interacts with the sample of the object, a clear image is formed.
- These are high resolution images and displayed on a computer screen.
Types of Electron microscopy –
- Scanning Electron Microscope (SEM)
- Transmission Electron Microscope (TEM)
[1]. SEM (scanning electron microscopy) –
- SEM technique is largely used for studying surface particles.
- An electron beam is constricted by magnetic lenses to give a thin (1-10nm) probe, which travels progressively point to point over a sample.
- Electrons scan the surface of the sample & the interaction of electrons with the surface generates several types of emission – 1).Secondary and Reflected electrons 2). Transmitted electrons. 3). X-ray showing-down Radiations. 4). Optical Radiations.
- These can be registered and converted into electrical signals. these signals are amplified and fed to cathode ray tube.
- So, images are formed on screen.
- This method is usually employed for particles measuring more than 5 nm.
- Electrons are generated from electron gun are in the range of 20kev to 30kev generally, for electrons with energy of 100kev the sample thickness should be about 50nm.
- Modern devices make it possible to obtain selective images for elements from Boron to Uranium with resolution of 0.5nm and selectively up to 10-20g which amount to, e.g. – 150 atoms for calcium.
Advantage of SEM –
- SEM gives the great body of information like- size, shape of particles.
- It gives information of their distribution and topology.
- This can observe nanostructures and atomic details.
- SEM is very useful in research about the cells, viruses and their internal structures.
Disadvantage – SEM takes long scanning time.
[2]. TEM (Transmission Electron Microscopy) –
- A sample shaped as thin film is transilluminated by a beam of accelerated electrons with an energy of 50-200kev in vacuum of 10-6 nm of Hg.
- In the Transmission electron microscopy, electrons pass through the sample.
- Those electrons that were deflected at small angles by atoms in sample are passed through the sample get into a system of magnetic lenses to form a bright field image of the sample internal structure on a screen and film.
- A resolution of 0.1nm was achieved, which corresponds to a magnification factor of 106
- The resolution depends on the nature of sample and method of its proportion.
- Usually, films of 0.01nm thickness are studied, the contrast range can be extended using carbon replicas.
- Modern ultramicrotomes allow obtaining sections 10-100nm thick. Metals are studied as thin foils.
- Transmission microscopes make it possible to obtain diffraction patterns, which provide information on the crystalline structure of sample.
Advantage of Transmission electron microscopy →
- TEM useful in research process of nanotechnology, and material science.
- It gives details about internal structure and shows internal parts of organelles & ultrastructure.
- TEM obtain very high resolution so we can observe structure at the atomic level.
- TEM helps to study about the virus, by using this easily can visualize very small particles like viruses.
Applications of Electron Microscopy →
- Electron microscopy helpful for analysis of nanoparticles and nanomaterials.
- It makes easier the study of metals and polymers, and helps to find the defects, cracks and structure.
- Electron microscopy is very helpful in the semiconductor industry; it helps in inspection of microchips and circuits.
- Electron microscope helps in the study of organelles (nucleus, mitochondria etc.) and helps for the observation of viruses and bacteria.
- This microscopy useful in the medical science for study of cancel cells and disease diagnosis and research, study about the drug development and pathology.
Electron microscopy is an advanced technique that has modernize the study of microscopic structures. By using electron beams instead of light, it provides high resolution and allow scientists to observe atomic level, cells and viruses.
Electron microscopy is the most advanced technique in modern science. Electron microscopy is very important and an essential tool in the modern science that really helps us to explore and understand the structure strongly beyond the limits of any other traditional microscope. Electron microscopy really plays a vital role in scientific research and technological advancement.
